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CELL DIVISION
As cells grow they must divide
Why?…(write your own answer)
DNA and cell division
Both daughter cells need a complete set of DNA,
nothing missing, nothing extra
DNA starts out as Chromatin (spread out DNA
molecules)
Chromatin turns into Chromosomes by the
process of Condensation (tightly folding)
Chromosomes
• Chromosomes are the structures that contain
genetic material we are passing from
generation to generation in our cells.
• Chromatin is the relaxed form of DNA in a
cell’s nucleus.
• Chromosomes are much more organized
than chromatin.
nucleus
DNA
Very, very long!
Wound up in a big
mess=Chromatin!
A very small
piece of a
chromosome=a
GENE!
Very Organized =
Chromosomes
How do we get
chromosomes from our
DNA?
CELL DIVISION
•
•
•
A Chromosome
1 chromatid
Centromere
2 Identical copies
CELL CYCLE
• Open book to pg 246
• Cell cycle is in 5 phases
• G1 ; S ; G2 ; M ; C
• G1 - Most of cell’s growth and activity
• S - DNA replicates
• G2 - Final preparations for division
• M - Nuclear division (mitosis) - Divided into 4 stages
• C - Cytokinesis - division of the cell
Nuclear membrane
INTERPHASE
Centrioles .
In between cell divisions
(G1 , S, and G2 phases)
Most of the cell’s life is in
interphase
Chromosomes are in the
form of chromatin
(diffuse and invisible)
Each DNA replicates
(makes a copy of itself)
Centrioles begin to move
to poles of cell
Astral rays
Aster
PROPHASE
Chromosomes
First stage of actual
mitosis
Chromatin condenses into
chromosomes
Nuclear membrane
disappears
Asters form at poles of cell
(Not visible in plants)
Astral rays connect to
centromeres on
chromosomes
Asters and Astral rays
together called the spindle
METAPHASE
Chromosomes are pulled
by astral rays
Chromosomes line up
along the equator of the
cell
ANAPHASE
Centromeres break
Each chromosome is
pulled apart into separate
chromatids
Spindle pulls chromatids
toward poles
TELOPHASE
Chromosomes disappear
Nuclear membranes
reappear
Spindle disappears
Cytokinesis -Cell
membrane divides cell into
2 daughter cells
(In plants cell wall forms
between daughter cells)
Daughter cells go back to
interphase
MITOSIS: ANIMAL CELL
MITOSIS: PLANT CELL
The Internet is full of great
Mitosis study tools….
http://www.youtube.com/watch?v=pOsAb
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